Just confirmed at Inside PlayStation 4: Building the Best Place to Play by Dominic Mallinson, VP, R&D, Sony Computer Entertainment America.

What is TrueAudio?

In a nutshell, TrueAudio is a return to the concept of hardware accelerated audio processing, with AMD leveraging their position to put the necessary hardware on the GPU. Hardware accelerated audio processing in the PC space essentially died with Windows Vista, which moved most of the Windows audio stack into software. Previously the stack was significantly implemented through drivers and as such various elements could be offloaded onto the sound card itself, which in the case of 3D audio meant having the audio card process and transform DirectSound 3D calls as it saw fit. However with Vista hardware processing and hardware access to those APIs was stripped, and combined with a general “good enough” mindset of software audio + Realtek audio codecs, the matter was essentially given up on.

Now even with the loss of traditional hardware acceleration due to Vista, you can still do advanced 3D audio and other effects in software by having the game engine itself do the work. However this is generally not something that’s done, as game developers are hesitant to allocate valuable CPU time to audio and other effects that are difficult to demonstrate and sell. Further complicating this is of course the current generation consoles, which dedicate a relatively small portion of what are already pretty limited resources to audio processing. As a result the baseline for audio is at times an 8 year old console, or at best a conservative fraction of one CPU core.

The Digital Sound Processor (DSP) is a dedicated bit of silicon that uses a scalable architecture of audio processing cores to parallelise audio effects computations, in a similar way to how graphics cards spread graphics calculations across hundreds of processor cores.

The reason for the DSP to be on a graphics card isn't entirely clear apart from being able to take advantage of the graphics pipeline's direct memory access, for high speed data retrieval. Seemingly the technology could just as easily be implemented on an APU or dedicated card too.

What TrueAudio isn't, however, is a sound card. It won't be taking over the output of audio but merely offsetting certain calculations, which would otherwise be too taxing to be left for just the CPU to do. These include effects like reverb and spatial audio as well as core functions like channel remixing and even just mp3 playback.

Realistically, both Xbone and PS4 audio chips should be fine for audio tasks. This proves that the PS4 chip isn't just an mp3 decoder as some people believed. In DBZ terms I'd say Android 17 and 18, both are sufficient and will produce great audio and effects.

This basically offloads complex audio calculations from the CPU to dedicated hardware. Like sound cards did back in the day.

Probably needed given the low power of the CPU's in these things. But it also means better sound occlusion and reverbaration, as well as probably better/more accurate 3D sound position and more audio sources for the final mix.